WALNUT CREEK — A Walnut Creek man was seen passed out behind the wheel of his truck at a stoplight and had been stopped by police shortly before he struck two pedestrians — killing one of them — outside a hotel in September, according to a prosecutor who on Wednesday filed felony charges against the driver.

Hossein Tabrizi, 54, is expected to be arraigned Thursday on charges of gross vehicular manslaughter while intoxicated in the killing of 52-year-old Santa Barbara resident Sherry Hicks, and intoxicated driving causing great bodily injury in the wounding of Hicks’ daughter-in-law, 24-year-old Sheng Hahn. The crash occurred about 6:15 p.m. Sept. 8 as the victims and their husbands were walking on a North Main Street sidewalk.

Toxicology test results show Tabrizi was intoxicated on the anti-anxiety prescription drug Lorazepam when he struck the women, according to the Contra Costa District Attorney’s Office. It is unclear whether he was prescribed the medication; Tabrizi told hospital staff members after the accident that he wasn’t taking any medication, and he has refused to talk to investigators, said Bruce Flynn, senior deputy district attorney.

Tabrizi’s attorney, William Gagen, said if his client did test positive for the drug, it may have been administered by a hospital after the accident.

“We have no reason to believe he was under the influence of anything based on what we know now,” Gagen said. “No one really seems to understand what happened, whether it was fatigue, whether he passed out, whether there was a medical issue.

“It’s not an easy case to unwind,” he said. “He was functioning well at work, and something happened on the way home that wasn’t the result of alcohol or partying.”

Gagen said Tabrizi turned himself in to the Walnut Creek Police Department on Wednesday afternoon. His bail is set at $250,000.

“About time” is how family friend Julie Scheibner reacted to the arrest. “I didn’t realize how heavily it’s been weighing on me. I’m so relieved to know that he is going to be off the street. He shouldn’t be on the street.”

Tabrizi had just finished his workday at a Newell Avenue tire shop when he was seen asleep behind the wheel of his Chevrolet Silverado pickup at a stoplight just 100 yards from his workplace, Flynn said. Other cars drove around the Silverado as several light cycles passed without it moving.

In one of those cars was a nurse who, concerned that Tabrizi was having a medical emergency, called 911. Another witness approached Tabrizi’s driver-side door and shook him awake, after which Tabrizi continued driving.

A Walnut Creek police officer, responding to the nurse’s 911 call, soon caught up with Tabrizi and pulled him over on the Interstate 680 onramp at Olympic Boulevard upon seeing him veer 1 or 2 inches into a neighboring lane, Flynn said.

The officer reported Tabrizi had no apparent signs of intoxication and did not appear to be having a medical issue. After Tabrizi passed a field sobriety test administered while he stayed inside his truck, he was allowed to drive away.

“(Tabrizi) did claim he was very tired and was just coming home from work,” Flynn said. “The officer asked if he was taking any medication, and he said no. The officer let him go, and five minutes later they got the 911 call (about the fatal accident).”

Walnut Creek police Capt. Tim Schultz declined to comment on aspects of the case Wednesday and referred all questions to prosecutors.

Hicks’ mother, Betty Schwartz, said police told the family about the traffic stop months ago. It was still hard for her to fathom Wednesday.

“It has always bothered me,” the Ontario resident said. “Why did they let him go?”

Hicks, a math teacher and mother of three, and her husband were in town visiting her son and daughter-in-law. The family was walking to the young couple’s apartment when Tabrizi, traveling at 43 mph, veered onto the sidewalk and struck the women before crashing into a planter wall outside the Marriott Hotel without ever braking. There were no other cars on the road when he lost control of his vehicle, Flynn said.

Hicks was killed in view of her husband and son, who weren’t injured. Hahn was hospitalized for more than a month with head injuries and torn knee ligaments.

Scheibner, the family friend who was bartending at the hotel that night, sat with Hahn until medics arrived. She described Hahn as “broken everywhere” but is amazed at her recovery. Hahn is now walking, and preparing to work again.

“She walks real poised,” Scheibner said. “She realizes how close she was to death.”

Tabrizi suffered only a scraped elbow.

“He claims no memory of the actual incident. He suffered no head injuries,” Flynn said. “The only conclusion I can draw is he passed out again, so we have him passing out twice in a 20-minute period.”

Tabrizi was twice arrested for driving under the influence and once for public intoxication in 2005 in Ventura County. Only one of the DUI arrests resulted in a conviction, according to the Ventura County District Attorney’s Office. His license was reinstated in late 2009, according to the state Department of Motor Vehicles.

One of the DUI arrests involved a solo-vehicle crash in which Tabrizi struck a cement divider, Flynn said.

The past six months have been a struggle for Schwartz, Hicks’ mother. The family welcomed a new addition, Decker Etherton, who was born just months after Hicks’ death. He would have been Hicks’ first grandchild.

“Every time I look at my great-grandson, I think my daughter would have been so happy,” Schwartz said. “Nothing is going to bring her back.”

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